1994 F-250 5.8 Auto I'm slowly trying to get what seems to be a fuel problem resolved. The symptom is a stumbling while just driving along. Loss of power, a little bucking, sometimes comes to a complete stop. But always starts up again, and often will run fine for days after. Switching from tant to tank seemed to help but no real sign that one tank worked better than the other. I changed the fuel filter a couple of times and that "seemed" to help. But the problem is so spastic it's hard for me to follow. The second, or third, fuel filter discharged a bunch of real dirty gas so I decided to fix that problem with brand new tanks with preinstalled fuel pumps,sender units and fresh filter. What a pain! I got the rear tank swapped out (Rockauto sent the wrong front tank so that will be later). Same problem - starts great, runs great -until it doesn't. Limps for a bit and then goes fine. Not using front (dirty?) tank. CEL is on and off, no apparent rhyme on reason, has been for years. O'Reilys couldn't get any signal on their code reader.

Any ideas?

Thanks, Bob

 

You can rule out the fuel system by borrowing a fuel pressure tester kit from O'Reilly's for free with a deposit.
here's how. https://www.ford-trucks.com/forums/1...rd-trucks.html

 

Thanks for the reply.
Yeah, I realized I left out the most important part - I did put on a fuel pressure test gauge. Got 40 psi after a few key on cycles, then 40 psi on start up, settling at 30 psi after a few seconds of running. Held pressure after shut down for at least 30 minutes until I removed gauge.

Bob

 

I’d have a look at the fuel venting. The Vapor canister and / or vent line to the tanks. When it quits, get out and take the gas caps off, see if the tank is under vacuum. It’ll hiss as you take the cap off. Quick and easy check.

Id also figure out why you can’t read codes. Try an innova 3145. Again, cheap and easy.

 

Maybe just me but that sounds like a TPS leaving the chat. Probably good idea to check for codes. Does it smell like it's running rich all the time? Also does the engine cut out at all? When it bucks on a scale of 1/10 how bad is it? I've had two crap out on me and when the first one went (only had the truck maybe three months) I made a turn, stepped on the gas, and was throwing me out of my seat (I'm a small guy) when it decided to buck.

 

JJF - So far, I can limp along and then it's running fine. That tells me it's not a vent issue. I'm gonna try OBSession's jumper to get the codes.

OB - No rich smelling. Not really "bucking", now that you press me. It has cut out completely a couple of times but not just quit. It usually feels like it misses two or three hits. then fires a few hits, then misses a few hits, and then clears up and runs fine. Sometimes it will finally die, but starts up again quite easily. When I get to where I'm going and shut it off, next time I need to go it's fine again, until it isn't.

Thank God, I usually don't drive in traffic.

 

Could also possibly an ignition issue. I had a miss/cutting out issue all summer where the truck would drop 100 to 300 RPMS and then shoot back up to the current RPM. Turned out to be a bad ICM. I have heard of a bad ICM cause a no start or random cut outs. My dad use to have an 89 F150 and he use to have to carry a spare ICM because it would randomly quit and be dead. One of two reasons I think my crapped out was either it's just another crappy part that fails a few months after a being installed or when my ECM died it zapped that module causing it to have issues. How's fuel economy? Does it seem to be worse than usual? When my ICM was going out my fuel economy went from 200 miles on one tank to barely 100 miles on one tank. They cause some really weird **** sometimes. Good idea for checking codes and go from there. I had no codes when I had issues but let's hope a code pops up making this process a little easier.

 

You gotta monitor the fuel pressure while you're accelerating or power-braking. Watching your fuel pressure at idle is meaningless because you're engine is sipping fuel at idle. You need to see your fuel pressure when your engine needs the most fuel.

 

Got that Prototype - I returned the gauge set-up but may circle back to it. It was just now misbehaving at idle after I tried to get the codes.

I tried the paperclip code reader, and got a couple of what looked like readable numbers but then it just went crazy - looked like 5-3-2-6-6 then 7-2-7 then flicker, then 3-4-1-1-1, etc. I did hear some relay clicking under the hood. Several clicks, no rhythm. What would that be?

So, I guess that since I get the flashes it means that I should be able to get the codes if I get to the right auto parts store-yes??

Another intermittent symptom - of something else I assumed, and wanted to keep it separate - is a high idle. Quite constant but occasionally will quiet down.

 

You have a 1994, so the computer will give you 3-digit codes. Like 5-2-2. Read the codes a few times and it'll become apparent the pauses between the numbers, and the pauses between the codes. It's normal to hear the relays click while it's testing out all the systems.
Since you can pull codes, a code scanner should work too. It takes a little bit of the guess-work out of it.

 

Break down & get one of these, either at one of the chains or online & save the frustration, $25-$35 bucks.



Good luck

 

Ford OBD I code reader on order.

 

Got the code reader like Scndsin's. Codes are; 56, 32, 67, 82, 91, 92, 94, 93, and 99. When it started repeating codes it got to the third one, 67 and stopped - just displayed 67 for several minutes. Repeated the test again and got exactly the same results-that made me feel that at least the test was legit. Can the reader only handle 12 codes at once?

Now I'm really confused. I've got a Chilton's, the Innova manual, and an online code list Ford OBD1 Codes List (Free Download PDF) - OBDCODEX. Of course they don't agree most of the time. The online seems more accurate. For example, Chilton's says codes 91,92,93,94 and 99 all have to do with E40D transmission - I have the C6, so I'm gonna ignore those for now, the trans seems to be working fine.

Code 32 - "EGR not responding properly - EVP" Also mentions EVP, EVR, and PFE I have the EGR blocked off, with the wires still connected, so assume this code is from that. No idea what EVP, EVR and PFE are.

Code 56 -"Vane Air Flow (VAF) on Mass Air Flow (MAF) sensor high" I'm gonna attack this first.

Code 91 - "System running lean-Fuel Control"
Code 91 - Transmission solenoid problem"
Code 92- "System running rich-Fuel Control"
Code 92 - "Transmission solenoid problem"
The trans is working fine, any idea why I get running lean and running rich at the same time?

Any better place to get code interpretation?

Thanks, Bob

 

A 94 F250-5.8 really, REALLY ought to spit out 3 digit codes.

Do you know anything about the computer? Ever seen the label on the connector?

Does the calibration code on the door frame still exist?

 

That exact Innova scanner can and will spit two AND three digit codes. It's just the way the scanner is set up. An example is an 11 code which means the system passed. As for the transmission part of things check your sticker in the door. It should give codes. An example is a truck with an E4OD factory will have an E under transmission.